Allowance for loan losses (Details) (Noncovered Loans [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	$ 107,699	$ 114,690
Charge-offs	(17,417)	(22,812)
Recoveries	5,438	5,794
Provision for noncovered loan losses	8,129	17,018
Allowance for loan losses, ending balance	103,849	114,690
Commercial Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	32,363	29,764
Charge-offs	6,703	(4,715)
Recoveries	545	526
Provision for noncovered loan losses	10,967	6,074
Allowance for loan losses, ending balance	37,172	31,649
Commercial Real Estate Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	31,857	32,026
Charge-offs	669	(1,851)
Recoveries	81	1
Provision for noncovered loan losses	(3,491)	2,952
Allowance for loan losses, ending balance	27,778	33,128
Commercial Construction Financing Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	5,173	7,180
Charge-offs	38	(1,358)
Recoveries	263	81
Provision for noncovered loan losses	(274)	1,736
Allowance for loan losses, ending balance	5,124	7,639
Finance Leases Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	341	475
Charge-offs	0	0
Recoveries	37	32
Provision for noncovered loan losses	(44)	(27)
Allowance for loan losses, ending balance	334	480
Installment Financing Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	17,981	21,555
Charge-offs	5,238	(8,091)
Recoveries	3,180	3,719
Provision for noncovered loan losses	(1,170)	3,526
Allowance for loan losses, ending balance	14,753	20,709
Home Equity Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	6,766	7,217
Charge-offs	2,324	(2,815)
Recoveries	645	699
Provision for noncovered loan losses	1,182	1,782
Allowance for loan losses, ending balance	6,269	6,883
Credit Card Receivables Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	7,369	11,107
Charge-offs	1,583	(2,318)
Recoveries	630	647
Provision for noncovered loan losses	104	(724)
Allowance for loan losses, ending balance	6,520	8,712
Residential Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	5,849	5,366
Charge-offs	862	(1,664)
Recoveries	57	89
Provision for noncovered loan losses	855	1,699
Allowance for loan losses, ending balance	$ 5,899	$ 5,490